The purpose of this paper is to discuss actual usage of the two Korean causal conjunctive suffixes, -(e)seand-(u)nikka, and to propose their multi-layered semantics based on analysis of corpus data. To account for the functional differences of the two conjunctives, most previous studies focused on different syntactic distributions or semantic contrast by employing an objectivist viewpoint, failing to incorporate the polyfunctionality, semantic overlapping and pragmatic ambiguities of them. This paper advances that the meanings of the two causal suffixes are distributed on four different cognitive-discourse levels: content, epistemic, speech act, and discourse level. Corpus analysis does reveal that all four levels are accessible to both conjunctive suffixes but the difference between the two suffixes lies in the different degree of accessibility of these four levels in their sentence semantics. This finding suggests that we treat these linguistic categories more flexibly by accepting their gradient and pragmatically ambiguous status.